I may consider buying the land up front - depending on what the real estate is doing in your area. I know in the Northeast prices are coming down as the boom is over. Beginning of next year will be a great time to buy but bad time to sell. This would essentially secure you a spot of land where you can build in the future. Also, if you decide you don't want to build then you can always turn around and sell it a couple years down the road for a likely profit.
Furthermore, I would suggest living with your parents for as long as possible and save save save!!! Take that money would have otherwise spent on rent/mortgage and deposit it. Just do something simple like open a money market account and let your money grow some in there until you are ready to buy/build. Whatever you think it will cost to buy/build add about 30% to that price. If you can handle the sticker shock then